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Quinacrine blocks PrP (106-126)-formed channels
Peter V Farrelly1, Bronwyn L Kenna, Karina L Laohachai
1Membrane Transport Group, Department of Chemistry, The Faculties, The Australian National University, Canberra City, Australian Capital Territory, Australia.
Journal of Neuroscience Research
|December 4, 2003
Summary
Quinacrine (QC) noncompetitively inhibits prion protein fragment (PrP[106-126]) cation channels by altering their kinetics, not conductance. This fast channel block mechanism may explain amyloid-induced membrane damage.
Area of Science:
- Neuroscience
- Biophysics
- Pharmacology
Background:
- Prion protein fragment (PrP[106-126]) forms cation channels implicated in amyloid-related membrane damage.
- Quinacrine (QC) is an acridine derivative known to inhibit ion channels.
Purpose of the Study:
- To investigate the mechanism by which quinacrine (QC) affects the kinetics of PrP[106-126]-formed cation channels.
- To determine if QC's action involves channel block and its potential pathophysiological significance.
Main Methods:
- Electrophysiological recordings of PrP[106-126]-formed cation channels.
- Dose-response and voltage-dependent analysis of QC effects.
- Kinetic parameter analysis (Po, Fo, To, Tc) and IC50 determination.
Main Results:
- QC acts as a noncompetitive channel inhibitor, altering channel kinetics without affecting maximal current (I).
- QC reduces mean current (I') by decreasing open probability (Po) and mean open time (To), while increasing mean closed time (Tc).
- Voltage-dependent effects were observed, with changes more pronounced at positive voltages, consistent with fast channel block at the channel mouth.
Conclusions:
- Quinacrine (QC) inhibits PrP[106-126] cation channels via fast channel block, primarily by altering channel gating kinetics.
- These QC-induced kinetic changes are concentration- and voltage-dependent.
- The findings suggest a potential mechanism for amyloid-induced membrane damage in vivo, mediated by these altered ion channels.